Group B streptococci are a major cause of neonatal sepsis and meningitis in the United States and other parts of the world (Anthony and Okada, Annu Rev Med., 28:355-69, 1977; Baker, Adv Intern Med., 25:475-501, 1980; Dillion et al., J Pediatr., 110(1):31-6, 1987). Prior to the 1990's, virtually all invasive group B streptococcal (GBS) infections were caused by serotypes Ia, Ib, II, and III. Reports of infection of newborn infants by a new serotype, type V, appeared in the pediatric literature in the 1990's (Greenberg et al., J Pediatr., 123(3):494-5, 1993; Hervas and Benedi, J Pediatr., 123(5):839, 1993; Rench and Baker, J Pediatr., 122(4):638-40, 1993). Infections caused by type V GBS were clearly becoming more common by the mid-1990's, and this serotype is now recognized as a common cause of infections in newborn infants and pregnant women (Zaleznik et al., Clin Infect Dis., 30(2):276-81, 2000). The capsular polysaccharide of type V GBS has structural features in common with other GBS capsular polysaccharides (CPS) but it is antigenically distinct (Wessels et al., J Biol Chem., 266(11):6714-9, 1991).